There may be a couple of rifle-clutchers roosting in their pet-peeve lookout post, ready to flame as soon as they see the whites of a strange eye, but most people, writers and readers alike, just get too much of a kick out of extra-cool eyes.

I, for one, could not resist Cool Eye Syndrome.
Syawn’s green eyes are grass-fresh and emerald-bright.
Mysst’s eyes are obsidian black, a rare color (does it even exist? I begin to despair of it!)
Rowtan’s eyes are popping blue against ebony skin (a common trait in his people, though enticingly unheard of on earth.)
And for some reason, it makes most readers and writers giddy to imagine such exotic eyes, however often it’s been done before.

We love cool eyes for the same reason we love sci-fi and fantasy:
Because they’re awesome, and we haven’t got them.